1. Field of the Invention
The present invention relates to workholding apparatuses and, more particularly, is directed to apparatuses for expanding the worksurface of a single precision workholding vise or a collection of precision workholding vises arranged on a common support member.
2. Description of the Invention Background
During the machining of a "workpiece" on a machine tool apparatus such as a milling machine or the like, single or multiple workpieces are typically held in place by a precision vise or clamping member ("a vise-like workholder") that is attached to the machine. Exemplary vise-like workholders that are adapted to hold a single workpiece are disclosed in U.S. Pat. No. 4,928,937 to Bernstein, U.S. Pat. No. 4,898,371 to Mills et al., U.S. Pat. No. 4,569,509 to Good, and U.S. Pat. No. 4,098,500 to Lenz. As can be gleaned from review of those patents, such vise-like workholders are adapted to clamp a workpiece between opposing jaw members operably supported on a base. Typically, one jaw member is fixed and the other jaw member is movable relative to the fixed jaw by means of a screw member housed within the base. As the movable jaw member is moved towards the fixed jaw member, the workpiece is clamped therebetween.
Other vise-like workholders are capable of holding two or more workpieces in side-by-side orientations. Examples of such "two-station" workholders are disclosed in U.S. Pat. No. 5,098,073 to Lenz, U.S. Pat. No. 5,094,436 to Stephan, III, U.S. Pat. No. 5,022,636 to Swann, U.S. Pat. No. 4,934,674 to Bernstein, and U.S. Pat. No. 4,529,183 to Krason et al. Such workholders typically comprise a base that has a central jaw fixed thereto. Two outer jaws are operably supported on the base and can be selectively positioned relative to the fixed central jaw by a vise screw that is operably received in a longitudinal cavity provided in the base.
The workpiece or workpieces are supported on the workholder bases of each of the above-mentioned workholders and are secured in position by at least two jaw members. The portion of the base upon which the workpiece is supported is known as the "worksurface" of the workholder. In many workpiece machining operations, it is desirable to use a workholder that is equipped with jaws and a worksurface that are at least as wide as the workpiece being machined to ensure that the workpiece is adequately supported during the machining operation. Moreover, with the ever increasing use of computer numerically controlled ("CNC") machine tool apparatuses, it is desirable to present as many workpieces as possible to the machining apparatus at a single time to reduce the amount of machine set-up and tool-change time. Thus, it is desirable to secure as many workpieces as practical between each pair of workholding jaws.
However, because the width of the worksurface and the jaws of the above-mentioned workholding vises cannot be "expanded" to accommodate wider workpieces or pluralities of workpieces, the user is forced to inventory a number of various sized workholders. Such workholders may typically cost several hundred dollars and, thus, the average machine owner cannot afford to maintain an extensive inventory of such workholding devices.
The above-mentioned problem has been somewhat addressed in U.S. Pat. No. 4,928,937 to Bernstein which discloses an arrangement of a plurality of workholders in an abutting, side-by-side relationship. Again, however, because the bases and jaw members of such workholding apparatuses cannot be expanded, numerous workholders must be used to accommodate wide or numerous workpieces.
U.S. Pat. No. 2,699,708 to Fotsch also discloses a solution to the above-mentioned problem by providing a machine tool table that has a plurality of T-slots provided therein that are adapted to slidably receive a corresponding number of clamping assemblies. While that arrangement enables a variety of different sizes of workpieces to be clamped in a desired position on the machine tool table, the clamping assemblies cannot be used on other machining apparatuses that are not equipped with a slotted table. Similarly, U.S. Pat. No. 4,898,371 discloses the use of several workholder bases placed side-by-side with a common "long" jaw blank placed therebetween for clamping long workpieces.
All of the above-mentioned workholding apparatuses have further disadvantages. In particular, during the machining of a workpiece, a machine tool is operably advanced into contact with the workpiece to remove a predetermined amount of material therefrom. As the machine tool contacts the workpiece, such removed bits and pieces of material, commonly referred to as "chips", collect on the workholder(s) and often become trapped in exposed slots and openings therein. If those chips are not cleaned from the workholder(s) prior to clamping the next workpiece(s), such chips can become jammed in various moving parts of the workholder(s) and possibly damage those workholder components. Thus, to prevent excessive wear and damage of the workholder components, the workholder(s) must be carefully cleaned and often completely disassembled to remove any chips, dirt or debris trapped therein. All of the aforementioned workholders have an exposed longitudinal slot that is notorious for collecting chips and other dirt and debris therein. Similarly, the T-slots in the work table of U.S. Pat. No. 2,699,708 must be carefully cleaned before the clamping assemblies are slidably inserted therein to permit precise location of the clamping assemblies and to avoid possible damage to those assemblies.
Workholding apparatuses have been designed such that the inner-workings of such apparatuses are substantially enclosed to retard the collection of chips and debris therein. For example, the screw member of the vise disclosed in U.S. Pat. No. 1,385,088 to Mellor is substantially protected from dirt and chips by being enclosed in the vise base. In this workholder design, the movable jaw support member or "nut" is adapted to be slidably positioned on the base by the screw member. However, the surface of the base upon which the support member slides is exposed. Thus, chips can accumulate on that surface and, ultimately, hamper the movement of the jaw support member on the base.
The problem of chip accumulation in the longitudinal slot of a vise-like workholder base has been somewhat addressed in European Patent Application Publication No. 0 526 432 A1, which was filed on Jul. 7, 1992 by CUTER S.p.A of Brescia, Italy. The workholder disclosed in that reference has a base that has a fixed jaw and a movable jaw. The base has a longitudinal slot or "groove" that extends its entire length for receiving a mobile jaw carriage and screw assembly. A series of notches are also provided along portions of the base adjacent to both sides of the groove for engaging a flanged portion of the screw assembly. To retard the infiltration of chips into the groove during machining, interconnected nylon blocks are placed in the groove. However, such blocks can be inadvertently separated from the base and lost during the installation and storage of the workholder. Also, such block assemblies do not prevent chips from collecting in the notches that are adjacent to the longitudinal slot. This patent also teaches the end-to-end attachment of the vise bases to create an elongated workholding member. However, that workholder configuration also has similar chip infiltration problems.
Another workholding apparatus that addresses the aforementioned chip infiltration problem is manufactured by Chick Machine Tool, Inc. of 500 Keystone Drive, Warrendale, Pa. 15086 under the trademarks "Bi-Lok", "Qwik-Lok", and "Multi-Lok". In that workholding device, a series of three overlapping movable cover plates are movably supported in opposing longitudinal grooves that are provided in the base on each side of the longitudinal groove therein. In particular, a "central" cover plate is movably supported in the grooves and movably attached to the movable jaw support members such that it always covers the otherwise exposed portion of the longitudinal slot extending between the movable support members. A second plate member is attached to one of the movable support members and is arranged to overlap the point of attachment wherein the center plate is movably attached to that movable support member. A third plate member is attached to the other movable support member and is arranged to overlap the point of attachment wherein the center plate is attached to that movable support member. Such overlapping arrangement of cover plates trapped within the base serves to completely cover the slot that extends between the movable jaw members. Although such workholder design effectively prevents chips from entering the workholder slot, it has some disadvantages. In particular, because the cover plates are captivated in opposed grooves provided in the workholder base and because the jaw members are movably supported on the top surface of the base, gaps are created between the cover plates and the jaw members. Such gaps are susceptible to the accumulation of chips therein which could hamper the positioning of jaw members on the base. Moreover, the time and tooling required to machine the opposing grooves in the base member increase the costs associated with manufacturing the workholder.
Also, those workholders that have clamping assemblies slidably received in a longitudinal slot provided in the base, are susceptible of having such clamping assemblies inadvertently advanced out of the base and possibly damaged. To prevent such possible damage, stops are typically provided to restrict the travel of the clamping assemblies. Those stops, however, must be removed each time the workholder is cleaned or serviced and, thus, increase the amount of time required to clean the chips that accumulate within the slot.
In view of the foregoing, there is a need for an apparatus that can be used in connection with vise-like workholders to expand the worksurfaces thereof.
There is another need for apparatuses that can be used in connection with multiple vise-like workholders to create a substantially continuous planar worksurface therebetween.
There is still another need for apparatus that can be used with a vise-like workholders that has the abovementioned attributes and also serves to protect the workholder's inner-workings and base member from chips and debris created during the machining process without hampering the workholder's operation.
There is a further need for apparatus that can be used in connection with vise-like workholders that can limit the travel of the workholder's clamping assembly without increasing the amount of time required to disassemble and clean the workholder.